Flavors and images

To launch an instance, which is just a virtual machine, you choose
a flavor and an image. The flavor represents the size of the instance,
including the number of CPUs and amount of RAM and disk space. An
image is a prepared OS installation from which you clone your
instance. When you boot instances in a public cloud, larger flavors
can be more expensive than smaller ones in terms of monetary cost.

To list the images that are available in your cloud, run some API calls: